MEASUREMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS|) IN DELHI

4.0 MEASUREMENT OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS|) IN DELHI

4.1 Sectoral Contribution and Impact of Increased Motor Vehicles on the Urban Environment :

The CPCB survey during 1988-89 five Metro cities account for 35% of total vehicular population in India. 2 Wheelers in 5 Metros only account for 23% of all Two Wheelers in India. Two-wheelers have grown in number accounting for 68.8% of all vehicles in 1995 against 8.8% in 1951 in India.

Delhi alone accounts 1/8^th of Total Vehicle Population (TVP) in India. The total number of vehicles in Delhi (27.0 lacs) was more than number of vehicles in cities of Mumbai (7.24 lacs), Calcutta (5.61 lacs) and Chennai (8.12 lacs) put together during 1995. The total no. of 2 W in Delhi (14.03 lacs) was about One and Half times of other three Metros i.e.Mumbai (2.46), Calcutta (2.22) & Chennai (4.61) put together during 1993.

Apart from increase in congestion and delays on the roads there has been an increase in air & noise pollution in Delhi due to increase in automobiles. The share of air pollution due to these vehicles in comparison to the total Urban air pollution have shot up with shot up with increase of vehicles as shown in table –15.

Table – 15 : Sectoral Contribution of Air Pollutants in Delhi

Source : PHD Chamber of Commerce & Industry, Report November 1991

The total number of vehicles has grown up to more than 30 lacs as on March 31, 1998 which has grown to more than 34.25 lacs as on July, 2001 (out of which CNG vehicle constitute 2450 Buses, 1178 Mini Buses, 27,263 Three Wheelers and 1993 Taxis). As on March 31, 2002 , 57,240 CNG vehicles were in operation which consist of 4231 Buses ( 2120 DTC & 2111 Private Buses) , 2165 RTV / Mini Buses , 35,678 Three Wheelers and 4816 Taxies . There are 94 CNG compressors which include 17 mother station on Indraprastha Gas Limited (IGL), 9 mother stations on DTC land, 13 on line stations, 26 daughter booster stations & 29 daughter stations to supply CNG in Delhi. Diesel vehicles constitutes only about 6% of total vehicles. Two Wheelers owing to predominate category (i.e. about 2/3^rd of total vehicular population ) in Delhi need utmost attention.

Gasoline consumption in Delhi has shown a growth of 247% during 1997-98 against 1980-81 as compare to Diesel consumption growth of 150% only.

Table – 16: Estimate of Demand of Transport Fuels in India (‘000 Tonnes)

Fuel share used in India is shown in figure-1 . Diesel is the predominant among all these fuels. It is also major contributor of PAHs emissions into the environment.

Figure -1: Fuel share used in India

4.2 Objective of PAH Monitoring in Ambient Air in Delhi :

Very few studies have been conducted in India & no background long-term data is available on these compounds in ambient air. Therefore, CPCB initiated systematic study on Particulate PAH at six NAAQM stations since mid of 1993 & also started respirable as well as total PAH monitoring at ITO since 1998.

4.3 Methodology of Measurement (Sampling & Analysis) :

This method is designed to collect particulate phase PAHs in ambient air and fugitive emissions and to determine individual PAH compounds. It is a high volume (1.2m³/min) method capable of detecting sub. ng/m³ concentration of PAH with sampling volume 480m³/min of air.

• Sampling of PAHs :

• Sample Extraction ,Processing & Analysis:

Samples were extracted with toluene using ultra sonic bath for about 30 minutes & repeated thrice for complete extraction . Alternatively sample can be extracted using soxhlet extraction apparatus for about 8 hours . Extracted samples are pooled & concentrated using rotary evaporator and further cleaned up with cyclohexane using silica gel column chromatography & finally analysed on gas chromatograph (GC) using capillary column (HP-Ultra-2, 30 m ) and flame ionisation detector (FID). Alternatively samples may be analysed using HPLC or more confirmatively with GC-MS.